This invention relates to polyethylene glycol derivatives which are novel and of use as a peptide-modifying reagent, peptides having amino groups which are modified by said polyethylene glycol derivatives, methods for production thereof and use of the modified peptides.
In recent years, with the development of research on proteins, a great number of peptides having various actions have been found. Owing to the progress of genetic recombination techniques and organic synthetic methods of peptides, it has become possible to obtain these physiologically active peptides and their structurally analogous compounds in a large amount. Many of these peptides having special activity are extremely useful as pharmaceuticals.
However, it is known that the clearance of peptides which have been administered in the circulatory system is generally very fast, and therefore improvement in durability of such peptides has been desired. Besides, since there is a risk of causing serious symptoms due to the production of antibodies in the case where the peptides are obtained from different species of animals or designed by peptide protein engineering, and they are different from those of humans in structure, improvement of the antigenicity of said peptides has been desired.
In order to use these peptides as pharmaceuticals, it is necessary to solve said problems in the aspect of their antigenicity and durability. The method of modifying the peptides chemically with macromolecular compounds is known to be extremely effective as the means by which to solve the above-mentioned problems.
Thus, polyethylene glycol derivatives have been widely used as peptide-modifying macromolecular reagents because they have excellent characteristics that they do not have immunogenicity themselves and that they do not affect the three-dimensional structures of peptides in aqueous solutions.
In modifying the amino groups at the N-terminal or in the side-chain of the lysine residues of the peptides using derivatives having one polyethylene glycol chain, there have been known a method wherein polyethylene glycol is introduced after conversion into an activated compound such as an acyl azide compound (Theodorus, Van Es. et al, Japanese Patent Publication (Kokoku) No. 23587/1981), the method with polyethylene glycol triazine derivatives [Frank F. Davis et al, J. Boil. Chem., 252, 3578-3581 (1977)], the method wherein an active ester of N-hydroxysuccinimide is used for introduction [Leonard M. et al, Tetrahedron, 40, 1581-1584 (1984), Abuchowski, A. et al, Cancer Biochem. Biophys., 7, 175 (1984)], the method wherein an activated compound introduced by carbonyldiimidazole is used [Charles, O. Beauchamp et al, Anal. Biochem., 131, 25-33 (1983)], the method with polyethylene glycol aldehyde derivatives [Fujino et al, Japanese Patent Unexamined Publication (Kokai) No. 178926/1986] and so on. In the meantime, as the method wherein derivatives having two polyethylene glycol chains are used, there have been known the method with polyethylene glycol triazine derivatives (Inada et al, Japanese Patent Publication (Kokoku) No. 42558/1986 and so on) and the method with polyethylene glycol triazine carboxylic acid derivatives (Yamazaki et al, Japanese Patent Unexamined Publication (Kokai) No. 316400/1989).
Despite the fact that derivatives having two polyethylene glycol chains are more effective in terms of reduction of antigenicity than those having one polyethylene glycol chain, [Inada et al, Japanese Patent Publication (Kokoku) No. 42558/1986, Inada et al, Chemistry Letters, 733 (1980), Inada et al., Seikagaku, 52, 1255-1267 (1980)], only triazine derivatives of Inada et al and Yamazaki et al as mentioned above are derivatives having two polyethylene glycol chains and are capable of modifying amino groups, which have been known so far.